BOSTON -- If anyone worried that the security of a rest-of-the-season deal might diminish Chris Johnson's hunger, then they don't know Chris Johnson.

After signing two 10-day pacts with the Boston Celtics, Johnson inked a contract Friday that will keep him here the remainder of the 2013-14 season and for as much as three years beyond that (though none of the final three years is guaranteed). Johnson is still trying to make an impression every time he's on the court, and good things are happening when he's on the floor because of that.

Johnson scored all 14 of his points on 4-of-6 shooting while connecting on four 3-pointers in the fourth quarter of Sunday's 102-91 loss to the Dallas Mavericks at TD Garden. Johnson was plus-12 in the fourth quarter and a team-best plus-7 overall for the day. He filled out his stat line with three rebounds, an assist, a steal and a block.

After breaking down how the Celtics let the game get away in a disastrous third quarter, Celtics coach Brad Stevens noted, "Maybe I should have played Chris Johnson more and earlier, and then we'd feel better about ourselves."

Chris Johnson blocks the shot of Mavericks point guard Devin Harris during the second half of the Celtics loss on Sunday. Mark L. Baer/USA TODAY Sports

Through 10 appearances, Johnson is plus-25 overall, second best on the team behind only Jared Sullinger (plus-35). Boston owns a team-best defensive rating of 97 when Johnson is on the floor, or 6.3 points better per 100 possessions than the team's season average.

What those numbers should tell you is that Johnson and his blur of activity are rubbing off on his teammates when he's in the game. Sure, it's not a very large sample size, but he is averaging 20.8 minutes per game and you most certainly know when Johnson is on the floor because he's forcing his teammates to meet his level of intensity.

Call it the Avery Bradley Syndrome. After a quiet rookie campaign, Bradley's confidence grew his sophomore season and the defensive tenacity he brought when he was on the floor was palpable. By the end of that season, Bradley had supplanted Ray Allen in Boston's starting lineup and was a key factor in the team's run to the cusp of the NBA Finals.

It's unfair to expect anything similar from Johnson, who is only 18 games into his NBA career on what amounts to four 10-day contracts thus far. There's still plenty of development ahead for the 24-year-old.

But Boston sees something in this 6-foot-6 swingman out of Dayton. There's potential there, exactly the sort that a team in transition can help nurture.

Sunday's game is a perfect example. Boston was lifeless in the third quarter and watched Dallas blow open the game. The Mavericks were up 23 with 9½ to play when Johnson subbed in to play shooting guard next to Rajon Rondo.

On that first possession, he missed a shot, hustled for his own rebound, and made the first of his four 3-pointers. Johnson was unrelenting throughout the frame. Like when Devin Harris got a step on him driving the lane late in the fourth quarter, Johnson recovered and blocked his shot.

Boston rallied as close as nine and, while it never really threatened, Johnson gave the Celtics something positive to pluck on a night the team's three-game winning streak got snapped.

Johnson is averaging 8 points, 2.6 rebounds, 1 assists and 0.9 steals in his 10 appearances. He's shooting 45 percent from the field and that number actually jumps to 45.9 percent beyond the 3-point arc.

He has found a sweet spot in the corners, where he's shooting a staggering 66.7 percent overall (12 of 18), blending a smooth stroke and a quick release that defenders are going to have to start respecting.

More importantly, he continues to impress his teammates, many of whom voiced support for keeping him around after his second 10-day contract expired on Thursday night.

The Celtics' roster could see another shakeup before the Feb. 20 trade deadline, which could open a greater opportunity for Johnson. For now, he must continue to make the most of available minutes.

Johnson has already endeared himself to Boston fans. Everyone likes an underdog, but his full-throttle style of play is exactly what many fans yearn for from some of his teammates who have the security of bloated, long-term contracts.

The Celtics used a piece of their mid-level exception to ink Johnson for up to four years. The fact that they were willing to sacrifice a little bit of roster flexibility and tip-toe a little closer to the luxury tax line to keep him here is no small reflection of what they think of him.

And by using the mid-level, Boston has put itself in fine position if Johnson does emerge as a role player on this team, his contract topping out at $1.05 million during the 2016-17 season.

The fact that the final three seasons are nonguaranteed makes it easy for Boston to cut ties (or use him as a trade asset down the road) if things don't work out. But the team would prefer to develop him and harness that energy he gushes on the floor.